Electronic Thesis and Dissertation Repository


Master of Science




Dr. Scott A. MacDougall-Shackleton


Seasonal changes in plasma corticosterone (CORT) levels indicate that birds modify their stress response through the year. Although this has been well documented, the method by which birds achieve this seasonality is not well understood. In this study I used house sparrows to determine if changes in glucocorticoid receptor (GR) immunoreactivity in several stress-related brain nuclei showed seasonal variation. The house sparrowsshowed seasonal variation in their stress response with baseline CORT levels being highest during the breeding season and lowest during winter. There was also significant change in plasma CORT post-dexamethasone during breeding, but not during other times of the year. In spite of the seasonal changes in CORT regulation there was no seasonal variation in the GR-immunoreactivity of brain regions involved in the stress response, such as the hypothalamus, nucleus taeniae of the amygdala, or hippocampus. These findings add to the growing research to understand the stress response.